1. Field of the Invention
The present invention generally relates to wet chemical surface processing of material objects such as semiconductor wafers, and more specifically to a method and apparatus for performing such surface processing using very small volumes of chemicals and without environmental pollution.
2. Description of the Related Art
Semiconductor substrate wafers must be prepared by cleaning, etching and other wet chemical processes before microelectronic devices can be fabricated in the surfaces thereof. The subject of surface preparation of wafers is presented in an article entitled "Wafer Cleaning: Can Dry Systems Compete", by R. Iscoff, in Semiconductor International, November, 1991, pp. 50-54.
Conventional wet chemical processes for cleaning and etching wafers are generally crude, utilize disproportionate volumes of chemicals, create environmental pollution and toxic waste disposal problems, require bulky and expensive support systems and use substantial amounts of electrical power. These processes include such expedients as squirt-bottle rinsing, beaker immersion, spraying and flushing under a running tap, and lack the precision, cleanliness and parametric control which is critical to consistently produce semiconductor wafer surfaces with the required purity, composition and crystal structure.
The chemicals used, especially acids, are highly toxic, and fume hoods, motor-driven air scrubber fans and other expensive and bulky equipment must be provided to remove vapors from the working environment. In addition, acid and base treatment facilities must be provided for reducing the toxicity of used chemicals prior to disposal.